I think they'll get around to that. A number of their UI nudges discourage people from taking a 'completist' view of reading their stream -- no mark-as-read, no

I think they'll get around to that. A number of their UI nudges discourage people from taking a 'completist' view of reading their stream -- no mark-as-read, no persistent latest-read-indicator, endless encouragements to follow more than could be read. That plus control of the client would let them offer some kind of paid pinning as a service.